The present invention generally relates to toner end detection apparatuses, and more particularly to a toner end detection apparatus of an image forming apparatus such as a laser printer, a copying machine and a facsimile machine which use a developing agent.
Generally, an image forming apparatus such as a laser printer which uses a developing agent (toner) is provided with a toner end detection apparatus. The toner end detection apparatus detects a toner end when a quantity of toner remaining within a toner tank becomes less than a predetermined value.
Conventionally, the toner end detection apparatus has an ultrasonic toner detection sensor which oscillates at a fixed oscillation frequency when the toner is adhered on a surface of the ultrasonic toner detection sensor and outputs a signal having a fixed level when a predetermined quantity of toner remains within the toner tank. The output signal of the ultrasonic toner detection sensor is supplied to an input port of a microcomputer, and the microcomputer detects the toner end by discriminating whether or not the ultrasonic toner end detection sensor is oscillating.
However, inside a developing unit, an agitator rotates at a predetermined period so as to uniformly distribute the toner. In addition, in order to prevent the toner from adhering on the surface of the ultrasonic toner detection sensor, a toner cleaning member is rotated in synchronism with the agitator.
For this reason, even when a sufficient quantity of toner exists within the developing unit, the ultrasonic toner detection sensor may erroneously detect the toner end because the no toner is adhered on the surface of the ultrasonic toner detection sensor and the ultrasonic toner detection sensor oscillates temporarily immediately after the agitator and the toner cleaning member pass the surface of the ultrasonic toner detection sensor.